Magnetic properties of Ga-doped lanthanum manganite with controlled oxygen stoichometry

Stoichiometric LaMnO₃ is an insulator whose A-type antiferromagnetic structure at low temperature is mainly connected to the Jahn-Teller distortion of the MnO₆ octahedra. The substitution of non magnetic d¹⁰ Ga³⁺ ions on the manganese site disrupts the orbital and spin orderings of the manganese ions and has a strong influence on the physical properties. The antiferromagnetic order is progressively destroyed while the ferromagnetic component increases. At the same time, the distortion of the orthorhombic cell decreases and the high temperature structural Jahn-Teller transition disappears. Such studies on manganese site substitutions give insight into the physics of the Mn-O three-dimensional network, which is supposed to be the key feature in the CMR manganites.